The invention of said prior application, Ser. No. 09/549,541, relates to a xe2x80x9csmartxe2x80x9d voltage regulator for regulating the voltage of an alternator which, in turn, provides a charging current to a storage battery for improving battery performance by maintaining a proper level of charge, and by reducing sulfation on the surface of the plates.
By way of background, motor vehicles in the United States some years ago typically had six-volt systems comprising, in part, a battery, a direct current (DC) generator, a DC starting motor or starter which, when energized, would start an internal combustion engine which, in turn, would drive the DC generator. A voltage regulator connected to the DC generator would control the output DC voltage thereof.
More recently, most motor vehicles in the United States use twelve-volt systems comprising a twelve-volt battery (12 volt being a nominal output voltage thereof), an alternating current (AC) alternator with appropriate rectifying means for providing a DC current, a DC starter, and a voltage regulator for controlling the voltage output of the alternator. Twelve-volt systems are described herein as a reference. The ""541 invention works equally well on any voltage system. The regulation set points are adjusted accordingly.
There are a number of uses or scenarios for the above-described 12-volt system, all of which are based on the internal combustion engine and lead-acid battery combination. One use is with xe2x80x9cover-the-roadxe2x80x9d trucks wherein the engines are operated more or less continuously for long periods of time, and thus, few start-up operations requiring battery current for starting are experienced. A large percentage of xe2x80x9cpassengerxe2x80x9d vehicles make fairly frequent starts (one or more per day) with sufficient run time between each start so as to keep the battery charged. On the other hand, there are a number of applications such as recreational boats, recreational vehicles, and antique and specialty cars wherein such vehicles are operated only occasionally, raising the likelihood of the storage battery used for starting the engine being significantly discharged throughout extended intervals during its life.
Another challenging application for a storage battery is in connection with vehicles that make long stops with loads left on, coupled with very little xe2x80x9crun timexe2x80x9d. For example, delivery vehicles serving a high-density business section of a metropolitan area typically make long stops with xe2x80x9cflashersxe2x80x9d left on, coupled with very little run time between stops. The result is storage batteries that are consistently undercharged, shortening the life of the batteries.
The ""541 invention actively monitors the needs of the above uses and changes the storage battery charging profile accordingly.
The goal of the present invention is to optimize battery and alternator life. By monitoring a lead-acid battery""s state-of-charge (SOC), and by monitoring the conditions the battery and alternator experience, the present invention appropriately adjusts the alternator""s output. Vehicle electrical loads are increasing each year (key-off and well as key-on); constant voltage regulators of the prior art are not able to optimally maintain battery health because battery needs vary widely from situation to situation. This results in batteries that are either overcharged (water loss) or undercharged (sulfation). Both situations significantly reduce battery life. The regulator means provided by the present invention works equally well in over-the-road trucks, as well as city delivery trucks, replacing specific voltage settings for specific vehicle use. The combination of high current and high heat can cause alternators to fail. The present invention regulator extends alternator life by preventing damaging combinations of alternator output current and alternator temperature.
There are, of course, numerous prior art voltage regulator systems for regulating the output voltage of the generator or alternator. Roseman, et al, U.S. Pat. No. 5,623,197 is an example of a prior art system which teaches the decreasing of the output voltage of the alternator when the battery is significantly discharged, to prevent excessive current from entering the battery. Roseman""s application concentrates on nickel-cadmium and sealed lead-acid aviation batteries charged by an aviation electrical generator/starter. The present invention concentrates on lead-acid batteries with very different needs.
Current industry technology emphasizes the constant potential method. This method has its disadvantages. It is difficult to have one optimal voltage setting for all conditions. If the voltage setting is too high, overcharging occurs, causing electrolysis (water use) and reduced battery life. If, however, the voltage is set too low, the battery remains undercharge for extended period, causing sulfation, and reduced battery life.
U.S. Pat. No. 5,703,476 suggests that basing the voltage setting on double slope temperature compensation charged the battery better. Temperature, however, is only one factor in the battery""s charging needs. Furthermore, battery temperature and regulator temperature are not often correlated. The physical placement of the battery is often different than the voltage regulator, resulting in poor temperature correlation.
The majority of voltage regulator prior art ignores the health of the battery, the primary role of the charging system. Tsuchiya, et al., U.S. Pat. No. 5,929,613, and Peter, et al., U.S. Pat. No. 5,773,964 are examples of this.
In broad terms, the ""541 invention provides a voltage regulator control which is capable of monitoring battery voltage, alternator voltage, voltage regulator temperature, battery temperature, and time. The regulator adjusts the charging profile based on the history of the foregoing five parameters. These parameters have varying importance depending upon the mode of the vehicle.
The primary purpose of the battery in vehicles is to start the engine. Discharged and failing batteries will have longer starts and lower minimum starting voltages. Therefore, it is wise to closely monitor and record voltage and time during starts. Minimum battery voltage during start, length of start, and the integral of delta voltage versus time may all be recorded by the present invention, and used to adjust charging profile. After the engine is started, the present invention charges the battery back as fast as possible without, however, damaging the battery or alternator. The regulator sets its first threshold (Tier D between 15 and 16 volts. It then records how long it takes to get to the Tier I threshold. This value (time) is used later to adjust the charging profile. Fully charged batteries take seconds to get to the Tier I threshold, while discharged batteries could take tens of minutes. The present invention lowers the system voltage before the risk of overcharging and damage occurs, thus achieving the goal of reaching Tier I threshold by charging the battery as fast as possible without overcharging. This feature also helps to break up sulfation on the battery""s plates.
The ""541 invention controller keeps the battery at the first threshold for a software-determined length of time depending on the battery state-of-charge (from multiple seconds to minutes).
The smart regulator will then regulate the battery""s voltage to a second threshold (Tier II). Tier II is in the voltage range of normal voltage regulators (14-15 volts). The regulator keeps the battery at Tier II for a period to ensure that the battery is fully charged, following which the controller tapers back the battery""s voltage to a final threshold, or safe-float voltage. This increases fuel economy, battery life, alternator life, and halogen light life. The float voltage is in the range of 13.5 to 14.2 volts, which is the range similar to over-the-road trucks that spend the vast majority of their time running, and not starting.
Application of the ""541 invention may include more than one of the described-above thresholds (Tier I, Tier II, Tier III, etc.), some of which may only be used when the controller deems it necessary based on the history of the system. Vehicles that have not run for an extended period are good examples of this. The controller may deem it necessary to add an extra high voltage phase (14.5 to 15.5 volts), in order to break up sulfation on the storage battery""s plates and ensure the storage battery is fully charged. This change in charge profile increases the life of storage batteries for recreational boats, recreational vehicles, and other infrequently driven vehicles.
Batteries that have an abnormally low open-circuit voltage are another example of where the controller may need to add an extra or extended high voltage phase (14.5 to 15.5 volts). Leaving headlights or electrical accessories on while the vehicle is not running induces this situation. Present vehicle charging systems are designed to keep storage batteries charged during normal use. They are not designed to fully recharge the storage battery. Often this results in storage batteries spending extended periods significantly discharge, resulting in storage battery plate sulfation and a reduction in battery life. The ""541 invention dramatically changes the charging profile to minimize this problem.
It is advantageous for the ""541 invention to communicate the information it collects about the charging system to the user and mechanic.
The ""541 invention controls a light in the vehicle""s dashboard or elsewhere. The light is flashed in two or more simple patterns. The first may indicate all charging parameters normal; the second pattern may direct the user to have the vehicle checked by a technician, thus giving users feedback before serious problems occur.
The technician is equipped with a hand held data-receiving device. The ""541 invention transfers all of the parameters it has recorded to the technician""s hand-held device. This is done through serial wire, optical sensor, wireless signal or other means. The hand-held device has software to analyze the data and recommend the technician""s next step. This tool will be invaluable for the technician""s diagnostic, debug, and preventative maintenance. Current charging system diagnostic tools only attempt to test the charging system""s current state. The ""541 invention gives the technician the ability to take into account the history of the charging system.
The present invention utilizes a battery""s state-of-charge (SOC) to optimize battery and alternator life. Determining a lead-acid battery""s SOC is more difficult while the vehicle carrying the battery is in use than while the vehicle is at rest, such as in a garage or parking area. The present invention provides a regulator that uses an algorithm designed around common patterns in automotive and/or truck vehicle use. The present invention is unique in how it determines the battery""s SOC. The present invention uses open-circuit voltage (OCV) and battery dynamic charge current to determine the battery""s SOC.